Position indicating devices



Feb. 11, 1964 J. R. PENDLETON ETAL POSITION INDICATING DEVICES Filed'June 2. 1960 3 Sheets-Sheet 1 Feb. 11, 1964 J. R. PENDLETO'N ETAL 3,121,146

' POSITION INDICATING DEVICES Filed June 2. 1960 3 Sheets-Sheet 2 Feb. 11, 1964 J. R. PENDLETON E ngL 3,121,146

POSITION INDICATING DEVICES Filed June 2, 1960 3 Sheets-Sheet 5 United States Patent 3,121,146 POSITION INDllQATlNG DEVICES Joseph Raymond Pendleton, Strettord, Manchester, and

Richard Smart, Urmston, Manchester, England, assignors to United Kingdom Atomic Energy Authority, London, England Filed June 2, 1960, fier. No. 33,589 Claims priority, application Great Britain June 12, 1959 9 Qlaims. ((Il. 2ss s7 This invention relates to position indicating devices.

According to the invention a device for indicating that a selected relative position is occupied by two relatively movable members has two magnet systems, one mounted on each member, and one magnet system comprises a single magnet with its poles orientated along the direction of relative movement of the members and the other system comprises a pivotally mounted indication operating member biased towards an undeflected position and a pair of magnets spaced apart on the indication operating member, one to either side of the pivot, like poles of the magnets of the pair being spanned by the single magnet when the members occupy the selected position so that the indication operating member is rotated to a deflected position.

One embodiment of the invention suitable for giving indication of the limit positions of shut oil? rods in a nuclear reactor will now be described with reference to the accompanying drawings in which:

FIG. -1 is a semi-schematic sectional elevation.

FIG. 2 is an isometric view of one half of the device.

FIG. 3 is a detailed sectional elevation of part of the device (divided into two parts).

As shown schematically in PEG. 1 a plate 1 forming part of the structure of a nucelar reactor supports a tube 2 containing a carriage 3 to which there is fixed a shut oil rod 4- and a primary magnet 5' having pole pieces 18 and 19. Two secondary magnet switch systems 6 and 7 are located one on each side of the plate 1 externally of the tube 2. The magnet switch systems 6 and 7 each comprises a slotted body tube containing two magnets lit and 11, fixed with like poles opposed, on an indication operating member in the form of a balance arm 9 rockable on a knife edge pivot 45. A yoke 43 of magnetic material with integral pole pieces 12a and 13a is also provided in association with pole pieces 12]) and 13b. The pole pieces 12b and 13a are each fitted with a non-magnetic biasing pin 70. A changeover switch 14 is operable by a pin 69 as the balance arm 9 rocks. The pole pieces 12!; and 13b are associated with yokes 2d of magnetic material extending to the tube 2 and the tubes 8 are joined by a conduit 1'7.

In FIG. 2 the tube 2 is shown partly cut away to expose the magnet 5 and the pole pieces '18- and 19. These pole pieces 18 and 1? have curved faces 21 matching the internal curvature of the tube 2. Four bolts 22. attach the magnet 5 to the carriage 3 which is of hexa onal tubular form. The magnet switch system 6 and the associated yokes 24 are shown in FIG. 2. (The magnet switch system 7 etc. is a duplicate of the magnet switch system 6.) The yokes 24 which are carried by a rectangular welded mild steel 'frame 23 are identical and each comprises a curved flux collector bar 26 of magnetic material clamped against the outer surface of the tube 2, a straight bar 27 of magnetic material welded at one end to the curved bar 26 and a curved pole piece 28 welded to the other end of the bar 27. The frame 23 has vertical side members 2? and horizontal side members 30. The yokes 24 are bolted to the horizontal side members 3%) by bolts 31. Side plates 32 on the frame 23 are held by channel section clips 33. The clips 33 airmen i atented Feb. 11, 1964 are held by the bolts 31 and are tack welded to the side plates 32. The body tube 8 shown in FIG. 2 is held in a clamp 34 formed by curved ends of the side plates 32 and a bridge piece 35 held by bolts 36. The bolts 31 holding the yokes 24 also locate a positioning plate 37. Electrical connection to the switch 6 is via a terminal box 16 and a rigid conduit 84.

Referring to FIG. 3 the magnet switch systems 6 and 7 have upper and lower end plates 38 which are circumferentially welded to the body tube 8. The pole pieces 12a and 12b are attached to a circular plate 59 by bolts 4i) while the pole pieces 13a and 13b are attached to a circular plate 41 by bolts 52. The pole pieces 112a and 13a are formed integral with the yoke 43. The knife edge 45 is fixed by bolts 46 at the centre of the yoke 4 5 and supports the balance arm 9'. The balance arm 9 includes a centre bearing block 47 having V- section bearing groove cs co-operat-ing with the knife edge 55. The magnets ill and ill are carried by arms as and Stl riveted to the bearing block 47. The arms 49 and 5d are formed from sheet metal blanks and include integral magnet locating frames 51. The magnets lo and ii are retained in the frames 51 by clips 52 fixed to the arms '49 and 5d by bolts 53.

The balance arm is held on the knife edge 49 by pin and nut combination 4 t A pin 54 screwed into the knife edge 45 passes through a hole 57 in the bearing block 47 and a nut 55 on the pin 5 holds the balance arm 9 through a washer 56 which bears against a secondary knife edge 5% on the bearing block 47.

The changeover switch 1 4 is carried by a support arm 6% fixed to the separate pole piece 13b by bolts as. The changeover switch 14- comprises a base block 59 of insulating material bolted to the support arm as by bolts 61. Three contact springs '63, 64 and 65 are carried by the block 5?. The contact springs 63 and 65 carry single contacts es and 68 respectively while the contact spring 64 carries a double contact '67 and the actuating pin 69.

The terminal box 16 has a cylindrical body 71. with upper and lower end plates 72. A socket 73 for a five pin plug 7a is carried by the upper end plate 72 and the live pin plug 74 is fitted to a flexible armoured cable 75 having high temperature resistant insulation. A five core temperature resistant lead 76 covered by an outer metal sheath 77 is contained within the conduit 34 connecting the terminal box dc to the switch system 6. Conductors 79, 8d, 551, 82. and 33 from the lead 75- connect with the socket 73 and pass into the body tube 8 of the switch system *6. The conductors 81, 82 and 33 connect respectively with the contact springs 6 63 and '65 of the changeover switch 14 and the conductors '79, and 88 pass through the body tube 3 to the conduit 17 which connects the body tubes 2; of the switch systems 6 and 7 (see FIG. 1). The conductors 79 and 31 are combined with a conductor $5 in a lead 36 covered by an outer metal sheath '87 contained within the conduit 17. The conductor '85 leads from the central contact spring 64 of the changeover switch 14- in the switch system 6. The conductors 7%, St} and 85 are connected respectively with the contact springs '63, es and 64 of the changeover switch 14- in the switch system 7. (See PEG. 1 which shows the switch system 7 although for the sake of clarity the electrical connections are omitted.)

In passage through the switch systems 6 and 7 all the conductors are insulated by ceramic beads The device operates as follows to give positional indication of the shut oil rod 4 which moves with the carriage 3 between limit positions in which the shut off rod 4 is either completely within the core of the reactor (in position) or is completely withdrawn from the core (out position).

Considering the shut oif rod 4 to be at an intermediate position in travel from the out to the in positions. In this case the magnet 5 is in a position having substantially no magnetic effect on the switch systems 6 and 7 so the balance arms 9 will both be in the undeflected position on account of the brass pins 7t) ensuring that a flux path of lower reluctance exists between the magnets lltl and 11 and the respective pole pieces 12a and 131) than between the magnets and the pole pieces 12b and 13a. The bias towards the undeflected position as exemplified by the switch system 6 in FIG. 1 is therefore imposed magnetically. The balance arms 9 are stable in this position because of the attraction between the magnets and Ill and the respective pole pieces 12a and 13b. The double contact 67 of each changeover switch 14 is held closed with the contact 63 by the balance arm 9 which presses on the pin 69. Thus an external indication circuit is completed to give indication of the intermediate position of the shut off rod 4 i.e. both switch systems 6 and 7 are in the same condition. When the shut off rod reaches the in position the magnet 5 is located spanning the yokes 24 associated with the switch system '7 (as shown in FIG. 1). The magnet 5 is arranged so that an N-pole influencing the magnet 10 of the switch system 7 is induced in the pole piece 121) and an S-pole influencing the magnet lit is induced in the pole piece 131). The S-pole of the magnet it) accordingly experiences an attraction towards the pole piece 12b and the S-pole of the magnet 11 accordingly experiences a repulsion from the pole piece 13b. Thus the balance arm 9 experiences a clockwise movement and is rotated until brought to rest in the deflected position by the pins 7 ii. The rotation of the balance arm allows the double contact 67 of the changeover switch 14 to break with the contact 68 and make with the contact 66 to complete an external indication circuit giving indication of the in position of the shut off rod 4. On movement of the shut off rod 4 from the in to the out position the magnet 5 moves with the carriage 3 to a posit-ion spanning the yokes 24 associated with the switch system 6. The balance arm 9 of the switch system 6 is rotated clockwise (as described above in relationship to the switch system 7) to operate the changeover switch 14 in the switch system 6 to complete an external indication circuit giving indication of the out position of the shut off rod 4.

The switch systems 6 and 7 reset automatically to the condition exemplified by the switch system 6 in FIG. 1 on removal of the influence of the magnet 5.

The device has an advantage in that it is operable at temperatures within a nuclear reactor up to about 600 C. The upper temperature limit above which the device is inoperable is dependent on the magnetic transition temperature of the magnetic material employed in the device.

We claim:

1. In combination with an assembly of two members movable relatively along a predetermined path, a device for indicating occupation by the members of a selected position and having two magnet systems, one of said systems comprising a single magnet mounted on one of said members with its poles orientated along the direction of relative movement of said members, and the other of said systems being mounted on the other of said members and comprising electrical switch means for opening and closing an indication circuit, a switch operating member rockable in a plane orientated along the direction of relative movement of said members about a pivot intermedi ate its ends and biased towards an undeflected position, and a pair of magnets mounted on said switch operating member, with like poles opposed, one adjacent each of the ends of said member, said pair of magnets being spaced apart such that like poles thereof are spanned by the poles of said single magnet of said one system to rock said switch operating member to a deflected position in said selected position of said members.

2. In combination with an assembly of twomembers movable relatively along a predetermined path, a device for indicating occupation by the members of a selected position and having two magnet systems, one of said systems comprising a single magnet mounted on one of said members with its poles oriented along the direction of relative movement of said members, and the other of said systems being mounted on the other of said members and comprising electrical switch means for opening and closing an indication circuit, a switch operating member rockable in a plane orientated along the direction of relative movement of said members about a pivot intermediate its ends, a pair of magnets mounted on said switch operating member, with like poles opposed, one adjacent each of the ends of said member, a yoke of magnetic material included in a magnetic circuit with said switch operating member and said pair of magnets mounted thereon and presenting pole faces respectively towards like poles of the magnets of said pair, and stop means defining a deflected position of said switch operating member in which position flux paths of differing reluctance exist between said pole faces and the respective magnets of said pair whereby to provide for said switch operating member a magnetic bias towards said undeflected position, said pair of magnets being spaced apart such that like poles thereof are spanned by the poles of said single magnet of said one system to rock said switch operating member to said deflected position in said selected position of said members.

3. The device according to claim 2 wherein said stop means comprises a piece of a non-magnetic material interposed between one of said pole faces and the respective magnet of said pair.

4. As an article of manufacture, a device for sensing the presence of a permanent magnet in a selected relative position and comprising a member rockable to a deflected position indicative of the presence of said permanent magnet in said selected position and biased toward-s an undeflected position, a fulcrum for said member, and individual permanent magnets mounted on said member one to either side of said fulcrum and spaced apart such that like poles of said individual magnets are presented to opposite poles of said permanent magnet to create a torque for rocking said member to said deflected position.

5. As an article of manufacture, a unitary construction of two encased devices respectively for sensing the presence of a permanent magnet in the limit positions of a predetermined path of relative movement thereof and comprising means to maintain a spacing between the encasements of said devices in accordance with the distance between said limit positions and, each of said devices, a member rockable to a deflected position indicative of the presence of said permanent magnet in the respective one of said limit positions and biased towards an undeflected position, a fulcrum of said member, and individual permanent magnets mounted on said member one to either side of said fulcrum and spaced apart such that like poles of said individual magnets are presented to opposite poles of said permanent magnet to create a torque for rocking said member to said deflected position.

6. A unitary construction of two encased devices according to claim 5 which is provided with tubular bodies as said encasements for said devices, rigid conduit means joining said bodies to maintain said spacing, electrical switch means included in each of said devices and operable by the respeotive rockable member for opening and closing a respective indication circuit, and electrical conductors leading to the switch means of one of said devices through the tubular body of the other of said devices and through said conduit means.

7. In combination with an assembly of two members movable relatively along a predetermined path, a device for indicating occupation by the members of a selected position and having two magnet systems, one of said systems comprising a single magnet mounted on one of said members with its poles orientated along the direction of relative movement of said members, and the other of said systems being mounted on the other of said members and comprising electrical switch means for opening and closing one indication circuit, a switch operating member rockable in a plane orientated along the direction of relative movement of said members about a pivot intermediate its ends and biased towards an undeflected position, yokes of magnetic material extending in laterally projecting relationship to said switch operating member respectively to locations at which the poles of said'single magnet are situated when said members occupy said selected position, pole pieces respectively adjoining the ends of said yokes adjacent said switch operating member, and a pair of magnets mounted on said switch operating member, one adjacent each of the ends of said member, to present like poles towards said pole pieces such that when said members occupy said selected position said single magnet causes said switch operating member to be rocked to a deflected position. Y

8. In combination with an assembly of two members of which one is tubular and the other is movable therein, a device for indicating occupation by the movable member of a selected position and having two magnet systems, one of said systems comprising a single magnet mounted on said movable member with its poles orientated along the direction of movement thereof, and the other of said systems being mounted externally of said tubular member and comprising electrical switch means for opening an indication circuit, a switch operating member rockable in a plane orientated along the direction of movement of said movable member about a pivot intermediate its ends and biased towards an tlndeflected position, yokes of magnetic material extending in laterally projecting relationship .to said switch operating member, flux collector bars adjoining the ends of said yokes adjacent said tubular member and embracing in part the outer periphery of said tubular member respectively at locations at which the poles of said single magnet are situated when said movable member occupies said selected position, pole pieces respectively adjoining the ends of said yokes adjacent said switch operating member, and a pair of magnets mounted on said switch operating member, one adjacent each of the ends of said member, to present like poles towards said pole pieces such that when said movable member occupies said selected position said single magnet causes said switch operating member to be rocked to a deflected position.

9. In combination with an assembly of two members of which one is tubular and the other is movable therein between limit positions, a device for indicating occupation by the movable member of the limit positions and comprising a single magnet mounted on said movable member with its poles orientated along the direction of movement thereof, two tubular bodies mounted externally of said tubular member, rigid conduit means joining said bodies and maintaining a spacing therebetween, a pair of yokes of magnetic material extending laterally between said tubular member and each of said bodies, flux collector bars respectively adjoining the ends of said yokes adjacent said tubular member and embracing in part the outer periphery of said tubular member at locations at which the poles of said single magnet are situated in the limit positions of said movable member, pole pieces respectively adjoining the ends of said yokes adjacent said bodies, and encased within each of said bodies an electrical switch means for opening and closing an indication circuit, a switch operating member rockab-le in a plane orientated along the direction of movement of said movable member about a pivot intermediate its ends and biased towards an undeflected position, and a pair of mamiets mounted on said switch operating member, one adjacent each of the ends of said member, to present like poles towards the pole pieces of the respective pair of said yokes such that when said movable member occupies the respective limit position said single magnet causes said switch operating member to be rocked to a deflected position, electrical conductors for one of said switch means being passed through the tubular body encasing the other of said switch means and through said conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 2,467,073 Binford Apr. 12, 1949 2,671,834 Kniecik Mar. 9, 1954 2,694,171 Campbell Mar. 9, 1954 2,726,296 Hanson et al Dec. 6, 1955 2,843,697 Beck July 15, 1958 

1. IN COMBINATION WITH AN ASSEMBLY OF TWO MEMBERS MOVABLE RELATIVELY ALONG A PREDETERMINED PATH, A DEVICE FOR INDICATING OCCUPATION BY THE MEMBERS OF A SELECTED POSITION AND HAVING TWO MAGNET SYSTEMS, ONE OF SAID SYSTEMS COMPRISING A SINGLE MAGNET MOUNTED ON ONE OF SAID MEMBERS WITH ITS POLES ORIENTATED ALONG THE DIRECTION OF RELATIVE MOVEMENT OF SAID MEMBERS, AND THE OTHER OF SAID SYSTEMS BEING MOUNTED ON THE OTHER OF SAID MEMBERS AND COMPRISING ELECTRICAL SWITCH MEANS FOR OPENING AND CLOSING AN INDICATION CIRCUIT, A SWITCH OPERATING MEMBER ROCKABLE IN A PLANE ORIENTATED ALONG THE DIRECTION OF RELATIVE MOVEMENT OF SAID MEMBERS ABOUT A PIVOT INTERMEDIATE ITS ENDS AND BIASED TOWARDS AN UNDEFLECTED POSITION, AND A PAIR OF MAGNETS MOUNTED ON SAID SWITCH OPERATING MEMBER, WITH LIKE POLES OPPOSED, ONE ADJACENT EACH OF THE ENDS OF SAID MEMBER, SAID PAIR OF MAGNETS BEING SPACED APART SUCH THAT LIKE POLES THEREOF ARE SPANNED BY THE POLES OF SAID SINGLE MAGNET OF SAID ONE SYSTEM TO ROCK SAID SWITCH OPERATING MEMBER TO A DEFLECTED POSITION IN SAID SELECTED POSITION OF SAID MEMBERS. 